Refining hydrocarbon oil



F Drawing.

Patented Mar. 7, 1933 UNITED STATES PATENT OFFICE STEWART S. KURTZ, JR, OF MERION, PENNSYLVANIA, ASSIGNOR TO THE ATLANTIC BEFINING COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA The present-invention relates to the art of mineral oil refining, and has particular reference to the separation of crude petroleum or petroleum products into fractions of different chemical compositions while of approximately the same distillation range.

In accordance with my invention, crude petroleum or petroleum products, particularly oils of substantial viscosity, are separated into various fractions by means of fractional extraction with an aromatic cyanide, such as benzonitrile.

It is recognized in the art that mineral oils, such as petroleum, comprise essentially a mixture of hydrocarbons of various groups of homologous series or compounds, such for example, as paraflins of the general formula CnH n+2, olefines of the general formula CHI-I211, hydroaromatics and polymethylenes of the same empirical formula, and various other series of compounds of chain and/or ring structures in which the hydrogen to carbon ratio is less than the foregoing series. A. large number of individual compounds of each series and of difiering boiling points are present in petroleum.

The various types of crude petroleum,

which are generally classified into three groups, namely, paratfin base, naphthenic or asphaltic base, and mixed base, contain the various series of hydrocarbons mentioned heretofore in difierent proportions. For example, in the parafin base crude oils, such as those obtained from the oil fields of Pennsylvania, there is a relatively high proportion of hydrocarbons having a chain structure and a high hydrogen to carbon ratio. whereas in the naphthenic or asphaltic base crudeoils there is a relatively large proportion of hydrocarbons having ring structures and a low hydrogen to carbon ratio. Mixed base crude oils, such as are obtained from the Mid-Continent oil fields, contain hydrocarbons in proportions intermediate these two extremes.

As the use of viscous petroleum oils is almost entirely physical, the above described chemical nature of those oils is important in reflecting certain physical characteristics.

The variance in the proportion of the dif- REFINING HYDROOARBON OIL Application filed January 23, 1931. Serial No. 510,847.

ferent series of hydrocarbons in paralfinic, naphthenic, and mixed base oils is evidenced by the physical properties of the various oils, and particularly by the relationship of the specific gravity to the viscosity of one oil as compared with another. For example, oil from a Pennsylvania crude with a viscosity of 400 seconds Saybolt Universalat 100 F., will show a specific gravity at 60 F.

in which G is the specific gravity at F, V is Saybolt Universal viscosity at 100 ll, and a is a constant known as the viscositygravity constant. Fractions from each of the difierent types of crudes have difl'erent viscosity-gravity constants. Such constants are lower for fractions of the parafinic crudes than are the constants for fractions of the naphthenic crudes. An article entitled The viscosity-gravity constant of petroleum lubricating oils by J. B. Hill and H. B. Coats which will be found in volume 20, page 64:]. et seq., Industrial and Engineering Ghemistry for June, 1928, explains the determination of the constant for several typical oils.

The viscosity-gravity constant is, there- G=a+ log (V- 38) fore, an index of the parafiinicity or naphthenicity of an oil, since when a given crude is distilled and fractions thereof are collected, regardless of the fraction upon which the specific gravity and the viscosity are taken, when such specific gravity and viscosity are substituted in the formula and the viscosityg-ravity constant determined, the constant will be substantially the same for each of the several fractions of the crude.

The viscosity-gravity constants of the vis--- cous fractions for some of the typical crudes are as follows: Milltown (Pennsylvania) 0.8067, Burbank (Mid-Continent) 0.8367, Guadalupe (Gulf Coast) 0.8635, Mirando (Gulf Coast) 0.9025.

These oils are increasingly paraflinic as the viscosity-gravity constants decrease.

I have found that oils containing both the paralfinc series of hydrocarbons and the various naphthenic series may be fractionally extracted with a suitable solvent such as an aromatic cyanide, and more particularly benzonitrile. The various series of hydrocarbons possess a differential solubility in this solvent, the naphthenic compounds being 7 more soluble therein than the parafiinic hydrocarbons. By means of extraction with benzonitrile, it is, therefore, possible to efiect a partial separation of the naphthenic compounds from the parafiinic, and to obtain from an oil containing both classes an oil which is much more paraflinic than the original oil, and one which is much more naphthenic. Bymy invention, for example, it is possible to produce an oil of the quality normally obtained from Appalachian crudes from crudes of the-mixed base type from the Mid-Continent area, and, conversely, to obtain oils from mixed base crudes such as are normally obtained from the naphthenic oils of the Gulf Coast area.

In practicing my invention, I prefer to mix the oil fraction to be treated with a suitable proportion of benzonitrile at a temperature sufliciently high that complete solution is effected' and a homogeneous liquid obtained. I

then cool the mixture to a temperature sufficiently low to cause a separation of the liquid into a two layer system, the upper layer being a solution of a relatively small amount of benzonitrile in the more parafiinic portion of the oil, and the lower layer comprising a solution of the more naphthenic portion of the oil in benzonitrile. Instead of this heating and cooling to effect extraction, I may simply agitate the mixture of liquid at normal temperatures. Where substantial quantities of solid hydrocarbons belonging to the true paraflin series ,CnH n+2 are present,

these solids or waxes remain in the upper layer, and may cause it to be solid or semisolid. Separation of the two layers is then efi'ected, for example, by decantation, and the benzonitrile removed from each of the separated oil layers by vacuum distillation or 4 other means, thereby obtaining two oils of similar distillation ranges but of widely different physical characteristics and correspondingly different chemical compositions.

, Before removing the benzonitrile from the upper and more parafinic layer of oil obtained in the above described process, I may add'a further "quantity of benzonitrile, and, repeat the process foran extraction of additional naphthenic'bodies from the oil. The extraction may be repeated any desired number of 'times, thereby producing oils of progressively increasing paratfimcity as evidenced by a decreasing viscosity-gravity constant. In wax-bearing oils, the final undissolved product is a mixture of solid and liquid hydrocarbons. While the exact chemical compositions of these compounds are not known, it is probable that the liquid hydrocarbons are branched chain hydrocarbons of the paraflin series, Whereas solid bodies are straight chain paraffin hydrocarbons. This product may be further separated into solid and liquid hydrocarbons by any of the wellknown dewaxing processes, such as the cold settling process.

In many instances it will be found of advantage to dewax the oil prior to' the extraction process, as this expedites the manual operation of the latter.

My invention will be further understood from the following example: I I

100 parts of a previously untreated distillate obtained from a Gulf Coast crude oil and having a viscosity of 612 seconds Saybolt Universal at 100 F., a specific gravity .of 0.9303, and a consequent viscosity-gravity constant of 0.874 was heated to approximately 25 C. with an equal volume of benzonitrilel The homogeneous liquid. which resulted from this heating was cooled to 10 C., and allowed to settle, whereupon a two-layer system formed whichconsisted of an upper undissolved oil layer comprising 50 parts of the mixture, and a lower benzonitrile dissolved layer comprising 150 parts of the mixture. After separation, the layers were each freed from benzonitrile by vacuum distillation. The benzonitrile dissolved fraction {yielded 92 parts of benzonitrile and 58 parts of oil having a viscosity of 64.8 seconds Saybolt Universal at 210 F., a specific gravity of 0.9548, and a viscosity-gravity constant of 0.904. The undissolved fraction yielded 8 parts of benzonitrile and 42 parts of oil having a viscosity of 373 seconds Saybolt Universal at 100 F., a specific gravity of 0.8950, and a viscosity-gravity constant of 0.834.

From this example, it will be seen that by one benzonitrile extraction there has been obtained two oil fractions which are respectively higher in paraflinicity and naphthenicity than the original oil. By repetition of "denc d by progressively decreasing viscositygravity constants.

It is evident that by use of my process I am practically independent of the particular nature of the crude oil, but may produce viscous oils of any required characteristics from practically any type of oil.

For example, I am able, by my process, to

produce from petroleum of a mixed base t pe such as would, on normal batch distillatlon,

give a residuum of a viscosity of 150 seconds Saybolt Universal at 210 F. with a specific gravity of 0.928 or more, a lubricating stock with a viscosity at 210 F. of 150 seconds Saybolt Universal or more, and a specific gravity not higher than 0.910. This latter combination of properties is typical of cylinder stocks produced from Pennsylvania crude.

In extracting oils containing appreciable amounts of wax, the oil may be dewaxed, for example, by cold settling, prior to the extraction. The process is operable, however, in the absence of a preliminary dewaxing.

For brevity, in the appended claims, the term benzonitrile is employed in a generic sense to include that material and equivalent aromatic cyanides or mixtures thereof.

.WVhen herein and in the appended claims, an oil is specifically referred to as being viscous, it is to be understood that the oil is of substantially viscosity, i. e., having a' Saybolt Universal viscosity at 100 F., of the order of ,50 seconds and upwards.

WhatI claim is:

1. In the artof refining mineral oils containingparafiinic and naphthenic hydrocarbons, the process which comprises bringing the oil into contact with benzonitrile, thereby efiecting solution of a portion of the oil richer in-naphthenic hydrocarbons in the benzonitrile,separating the benzonitrile solution of oil from the oil so treated, and removing the benzonitrile from each of the fractions so obtained, thereby to obtain fractions of the oil respectively richer in paraflinic and naphthenic hydrocarbons.

2. The process of separating mineral oils containing paraflinic and naphthenic hydro carbons into fractions, which comprises bringing the oil into contact with benzonitrile, thereby effecting solution of aportion of the oil richer in naphthenic hydrocarbons in the benzonitrile, separating the benzoni- 'trile solution of oil from the oil so treated,

and distilling the benzonitrile from each ofthe fractions so obtained, thereby to obtain fractions of the oil'respectively richer in parafiinic and naphthenic hydrocarbons.

3. In the art of refining mineral oils containing paraflinic and naphthenic hydrocarbons, the process which comprises bringing the oil into contact with benzonitrile, thereby efiecting solution of a portion of the oil richer in naphthenic hydrocarbons in the benzonitrile, separating the benzonitrile solution of oil from the oil so treated, and retreating the treated. oil with additional benzonitrile.

4. In the art of refining oils containing paraflinic and naphthenic hydrocarbons, the process which comprises adding benzonitrile to the oil, heating the mixture to such a temperature as to efiect solution, cooling the solution to form a two layer system, and separating the upper layer from the lower layer.

5. In the art of refining mineral oils containing parafiinic and naphthenic hydrocarbons, the process which comprises adding benzonitrile to the oil, heating the mixture to sucha temperature as to efl'ect solution, cooling the solution to form a two-layer system, removing the lower layer, and similarly retreating the upper layer with benzonitrile.

6. The method of producing paraflinic lubricating oil from mixed base crude, which comprises distilling the crude and bringing a portionthereof into contact with benzonitrile, thereby partially dissolving the oil, separating the benzonitrile solution of oil from the oil so treated, and removing the benzonitrile from the treated oil.

7. The process of producing a lubricating I taining para-flinic and naphthenic. hydrocarbons, the process which comprises separating the oil into fractions respectively richer in parafiinic and naphthenic compounds by extracting said oil with benzonitrile.

9. In the art of refining mineral oils containing paraffinic and naphthenic hydrocarbons, the process which comprises fractionally extracting the oil with benzonitrile to produce fractions of the oil respectively richer in paraflinic and naphthenic compounds.

10. In the art of refining mineral lubrieating oil containing paraflinic and naphthenic hydrocarbons, the step of fractionally extracting the oil with benzonitrile to efiect a separation of fractions respectively richer in paraflinic and naphthenic compounds.

11. The process of producing a lubricating "stock of specific gravity less than .910 and of Saybolt Universal viscosity greater than 150 seconds at 210 F., from a crude petroleu m whlch on normal distillation yields a residuum of 150 seconds Saybolt Universal viscosity at 210 F., and a specific gravity greater than .928, which comprises separating a residuum from said crude petroleum and thenic hydrocarbons into fractions which are respectively richer in naphthenic hydrocarbons and paraflinic hydrocarbons other than Wax, the step which Comprises extracting the oil with benzonitrile.

13; In a prodess for separating viscous mineral oil, liquid at ordinary temperatures, containing paraffinic and naphthenic hydrocarbons, into fractions respectively richer in paraifinic and naphthenic hydrocarbons, the step which comprises extracting the oil with benzonitrile.

14. In a process for separating a substantially wax free viscous mineral oil containing paraffinio and naphthenic hydrocarbons into fractions respectively richer in paraflinic vand naphthenic hydrocarbons, the step which comprises extracting the oil with benzonitrile.

15. The process of treating a viscous fraction of a crude oil of one type containing para-ifinic and naphthenic hydrocarbons to procure a fraction having the quality of a corresponding fraction of a crude oil of different type having a greater content of paraffinic hydrocarbons, whichcomprises extracting the viscous fraction with benzonitrile, and separating the oil so treated into portions respectively richer in paraffinic and naphthenic hydrocarbons.

1,6. The process of treating a viscous fraction of a mixed base crude oil to procure a fraction having the quality of a corresponding fraction of a paraflinic base crude, which comprises extracting the viscous fraction with benzonitrile, and separating the oil so treated into portions respectively richer in paraffinic and naphthenic compounds.

17 In the art of refining mineral oils, the process which comprises adding benzonitrile to a viscous oil, liquid at ordinary temperatures, containingparaflinic and naphthenic hydrocarbons, heating the mixture to a temperature sufficient to effect solution, cooling the solution to a temperature suflicient to form two layers respectively richer in naphthenic hydrocarbons and paraflinic hydrocarbons other than wax, and separating the upper layer richer in paraflinic hydrocarbons from the lower layer richer in naphthenic hydrocarbons.

18. In the art of refining mineral oils, the

process which comprises adding benzonitrile to a viscous oil, liquid at ordinary temperatures, containing paraflinic and naphthenic hydrocarbons, heating the mixture to atemperature suflicient to efl'ect solution, cooling the solution to a temperature suflicient to form two layers, separating benzonitrile and paraflin wax from-the upper layer, and separating benzonitrile from. the lower layer to produce one fraction richer in parafinic and in naphthenic hydroa second fraction richer carbons than said viscous oil.

In testlmon whereof I affix TEWAR'I S.

my-signature. KIIRTZ, J18;

memes "hydrocarbons and paraffinie ,hydroearbons,

,Patent' dated -.Mareh 7,- 1933'; Disclaimer filed February 15 1 934, by-thg' assignee; I'I'wAtlant'icj Refin'ingCompany J Enters "this disclaimer, to

Petitioner disclaims from the scop'e'that the description in said 'patrentgi ves to the claims of said patent, the processv of extraction with benzonitrile (C H CN) of j either a viscous mineral oil containing'paraffinic and naphthenic hydrocarbons, or a viscous mineral oil liquid at ordinary temperatures and containing paraflinicfand naphthenic hydrocarbons, to produce fractions respectively richer naphthefnic [Ofiic'ial Gazette March/6,1934] 

